Sign holder base



FIG. 1 is a front elevational view of a sign holder base illustrating mynew design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is an enlarged perspective view thereof.

In the drawings, the broken lines represent environmental structureforming no part of the claimed design.

The ornamental design for a sign holder base, as shown and described.